The present invention relates to a servo control apparatus having functions to control position, velocity or force and having a programming or teaching function for use in, for example robot manipulators, machine tools and XY tables.
Conventionally, when teaching a position to a control object, driving of a mechanical actuating system is temporarily stopped to hold an actuator in a nonexcited state and the control object is manually displaced. Accordingly, since the control object bears a load due to the force of gravity etc., the the force of gravity must be compensated for by means of a bias spring or counter balance. On the other hand, when teaching is done by exciting the actuator to directly drive the object, a force sensor etc. is used to measure an external force and to feed back the measured external force.
However, the mechanical structure becomes complicated when providing in the structure a balance mechanism to compensate for the force of gravity, resulting in increased weight and cost. Further there is a limit in drive performance resulting in great force being required to displace the control object under the nonexcited state. Moreover, if the mechanical structure has a relatively great velocity reduction rate, it would be difficult to drive the control object.